Process for preparing superior high solids coatings

ABSTRACT

According to one aspect of the present invention, an improved method for preparing acrylic copolymer resins is provided in which the polymerization solvent comprises an alkanoic acid alkyl ester having a total of from about 7 to 18 carbon atoms per molecule. The monomers comprise hydroxy-substituted alkyl (meth)acrylates, and non-hydroxy substituted alkyl (meth)acrylates, and the process provides an improved method for forming low molecular weight acrylic resins useful as components in high solids acrylic coatings suitable for electrostatic spraying. The polymerization solvent can remain in the resin to become the solvent employed in the higher solids coating containing the thus-formed acrylic resins and provides surprisingly improved electrical resistivity and solvency and decreased surface tensions over prior art polymerization solvents. In accordance with another aspect of the present invention, an improved method for preparing high solids acrylic resin coatings is provided wherein an acrylic copolymer resin is dissolved in a coating solvent comprising at least one alkyl alkanoic acid ester having a total of from 7 to 18 carbon atoms per molecule.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 701,680, filed 2-14-85,now U.S. Pat. No. 4,638,031 which is a continuation-in-part ofco-pending U.S. Ser. No. 558,953, filed Dec. 7, 1983, now U.S. Pat. No.4,532,294.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a process for making acrylic coatingresins and more specifically to superior solvents useful in thesynthesis of high solids acrylic coating resins.

2. Description of the Prior Art

A large variety of acrylic coating compositions are known. Low solidscoatings, i.e., those containing about 18 to 40 wt.% solids and thebalance solvents, have heretofore been developed in which the resinsthemselves are characterized by high molecular weights, e.g., molecularweights in the range of 20,000 to 40,000. Such high solventconcentrations are required with these high molecular weight resins inorder to supply flowability and other properties necessary for ease inapplying a uniform coating. Due to strict air pollution regulations,pollution abatement of solvents is of paramount importance. To this end,the industry has expended much effort in an attempt to developelectrostatically sprayable coatings containing high solids contents,that is, coatings having a lower amount of solvents in order to satisfypollution regulations. Attempts to achieve high solids coatings bymerely using more of the conventional high molecular weight resins inthe coatings have not been successful since the increased solids contentusing these resins results in an unacceptably high viscosity, and oftenthe larger amounts of the resins cannot themselves be dissolved. Effortsat developing a "super solvent" for these conventional high molecularweight resins have also not proved to be successful. Therefore, coatingscontaining low molecular weight resins (e.g., for about 1,000 to 7,000weight average molecular weight) would be desirable in high solidscoatings in order to reduce the amount of solvents necessary in theblending for coating applications and, hence, the pollution difficultiesassociated with the solvents themselves. These high solids acryliccoatings are useful as exterior finish for automobiles, trucks, metalfurniture, and as an appliance finish.

In U.S. Pat. No. 3,267,057, a polar solvent of high dielectric constant(greater than 8, preferably from 20-40) is employed with oil modifiedalkyd resins. However, adequate leveling was not achieved by theseinventors in spraying of 67 wt.% solids coatings containing butylacetate when sprayed by electrostatic atomization.

U.S. Pat. No. 3,348,965 discloses alkyd resin compositions which arecapable of being sprayed electrostatically and incorporates polarorganic solvents (butyl acetate is so classified) in its sprayablecomposition to increase conductivities.

U.S. Pat. No. 3,796,590 is directed to acrylic solution coatingcompositions which can be applied by electrostatic spraying employingsolids contents of from 40 to 65 wt.% and organic solvents comprisingaromatic hydrocarbon solvents alone or in combination with certainalcohols. Portions of butyl acetate are indicated as also being suitablypresent.

German Patent Publication No. 1,519,258 contains a disclosure (noexamples) to the use of esters as polar solvents in electrostaticsprayable alkyd compositions, which was apparently added to the lacquerby the German patentees to decrease resistivities. The sprayablecomposition contained from about 45-55% by weight solids.

K. K. Mitra, "Electrostatic Application of Paint", Paint India, vol. 29,no. 9, pp. 52-56 (1979) indicates that while non-polar solvents(aliphatic and aromatic hydrocarbons chlorinated solvents, terpenes,etc.) can be employed in electrostatically sprayable paints to increasebulk and resistivity, polar solvents are used to control resistivity.The polar group is said to include ketones, alcohols, esters, ethers,ether alcohols, and nitro paraffins.

Also illustrative of prior art, high solids acrylic resins are thosedisclosed in U.S. Pat. Nos. 4,276,212 and in European Patent ApplicationNos. 27,719; 29,339; 29,594 and 29,683.

Solvents which are indicated to be typical in these references (e.g.,those mentioned in European Patent Application No. 29,594) are: Toluene,xylene, butyl acetate, acetone, methyl isobutyl ketone, methyl amylketone, methyl ethyl ketone, butyl alcohol and other aliphatic,cycloaliphatic and aromatic hydrocarbons, esters, ethers, ketones, andalcohols.

U.S. Pat. No. 4,151,152 discloses fast setting polyurethane varnisheswhich can be applied by airless or electrostatic spraying, and disclosesesters as suitable high boiling varnish solvents. Included as suitableesters are hexyl acetate, iso-amyl acetate and cyclohexyl acetate.Highly concentrated solutions are prepared containing from 50 to 70percent solids which must then be diluted prior to use.

Also relevant is a brochure entitled "Hexyl Acetate for the CoatingsIndustry" (Enjay Chemical Company), published prior to 1980, whichdiscloses the use of hexyl acetate as coating solvent in certainspecific low solids acrylic coating compositions; in urethane coatings;in nitrocellulose coatings; and in baking enamels.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an improved method forpreparing acrylic copolymer resins is provided in which thepolymerization solvent comprises an alkanoic acid alkyl ester having atotal of from about 7 to 18 carbon atoms per molecule. The monomerscomprise hydroxy-substituted alkyl (meth)acrylates, non-hydroxysubstituted alkyl (meth) acrylates, and the process provides an improvedmethod for forming low molecular weight acrylic resins which are usefulas components in high solids acrylic coatings suitable for electrostaticspraying. The polymerization solvent can remain in the resin to becomethe solvent employed in the higher solids coating containing thethus-formed acrylic resins and provides suprisingly improved electricalresistivity, and solvency and decreased surface tensions over prior artpolymerization solvents.

In addition, the solvents of this invention provide the low-molecularweight acrylic resins over a wide range of temperatures. Certain of thesolvents allow the use of lower temperatures which give significantprocess advantages, among them lower energy requirements and ease ofpollution control, while other solvents (such as the higher alkyl estersolvents) of this invention have been found to result in polymers havingstill narrower molecular weight distributions. Surprisingly, thesolvents of this invention produce low molecular weight acryliccopolymers which are characterized by superior molecular weight andviscosity properties, and are therefore especially suited for use inhigh solids coatings.

In accordance with another aspect of the present invention, an improvedmethod for formulating high solids acrylic coatings is provided whereinan acrylic copolymer resin is dissolved in a coating solvent comprisingat least one alkyl alkanoic acid ester having a total of from 7 to 18carbon atoms per molecule.

The coatings thereby formulated have excellent flow properties, higherresistivities than prior art coatings containing ketones and whenapplied to surfaces provide high gloss and high impact strength in theas-applied coating.

DETAILED DESCRIPTION OF THE INVENTION

According to one aspect of the improved process of this invention,acrylic polymers are prepared by contacting under polymerizingconditions a hydroxy-substituted alkyl (meth)acrylate and a non-hydroxysubstituted alkyl (meth)acrylate in the presence of a free radicalpolymerization catalyst and a polymerization solvent comprising at leastone liquid alkyl alkanoic acid ester having a total of from 7 to 18carbon atoms.

The mono-esters suitable in this invention therefore comprise normallyliquid esters selected from the group consisting of compounds having theformula (I): ##STR1## wherein R¹ is a straight or branched chain alkylof from 1 to 6 carbon atoms, and R² is a straight or branched chainalkyl of from 1 to 13 carbon atoms, with the proviso that R¹ and R²together contain from 6 to 17 carbon atoms, and mixtures thereof.Exemplary of such ester solvents are hexyl acetates, pentyl acetates,pentyl propionates, isobutyl isobutyrate, heptyl acetates, methylpentanoates, ethyl pentanoates, pentyl pentanoates, ethyl hexanoates,butyl hexanoates, ethyl neopentanoate, methyl neoheptanoate octylacetates, nonyl acetates, decyl acetates, undecyl acetates, dodecylacetates, tridecyl acetates and the like.

Preferred ester solvents of this invention are normally liquid estersselected form the group consisting of compounds of the formula (II):##STR2## wherein R³ is a straight or branched-chain alkyl having from 5to 7 carbon atoms, and mixtures thereof. Exemplary of such preferredester solvents herein are penty acetates, hexyl acetates, heptylacetates, and octyl acetates. Especially preferred as esterpolymerization solvents are hexyl acetate and heptyl acetate.

Also preferred as ester solvents of this invention are normally liquidhigher alkyl esters selected from the group consisting of compounds ofthe formula (IIa) ##STR3## wherein R¹ is as defined above and R" is astraight or branched-chain alkyl having from 8 to 13 carbon atoms withthe proviso that R¹ and R" together contain from 9 to 17 carbon atomsand mixtures thereof. Preferred higher alkyl ester solvents are thosehaving the formula ##STR4## wherein R" is as defined above. Exemplary ofthis group of preferred higher alkyl esters are octyl acetates, nonylacetates, decyl acetates, undecyl acetates and dodecyl acetates,tridecyl acetates.

The term "normally liquid esters" as used herein is intended to refer toesters which are in the liquid state at ambient conditions (25° C., 1atm.). The ester solvents are preferably substantially free of water(more preferably having a water content of less than 0.5 wt.%) and tracemetals (more preferably having a trace metals content of less than 0.004wt.%). In addition, the ester solvent is most preferably substantiallyfree of alcohol (e.g., less than 0.6 wt.% alcohol), such as alcoholremaining from the process by which the ester solvents are produced(e.g., alcohols of the formula R² OH, wherein R² is as defined above),and is preferably characterized by a resistivity of at least 15 megohms,as determined by Ransburg resistivity meter.

The hydroxy-substituted alkyl (meth)acrylates which can be employedcomprise members selected from the group consisting of the followingesters of acrylic or methacrylic acid and aliphatic glycols: 2-hydroxyethyl acrylate; 3-chloro-2-hydroxypropyl acrylate;2-hydroxy-1-methylethyl acrylate; 2-hydroxypropyl acrylate;3-hydroxypropyl acrylate; 2,3-dihydroxypropyl acrylate; 2-hydroxybutylacrylate; 4-hydroxybutyl acrylate; diethylene-glycol acrylate;5-hydroxypentyl acrylate; 6-hydroxyhexyl acrylate; triethyleneglycolacrylate; 7-hydroxyheptyl acrylate 2-hydroxy-1-methylethyl methacrylate;2-hydroxy-propyl methacrylate; 3-hydroxypropyl methacrylate;2,3-dihydroxypropyl methacrylate; 2-hydroxybutyl methacrylate;4-hydroxybutyl methacrylate; 3,4-dihydroxybutyl methacrylate;5-hydroxypentyl methacrylate; 6-hydroxyhexyl methacrylate;1,3-dmethyl-3-hydroxybutyl methacrylate; 5,6-dihydroxyhexylmethacrylate; and 7-hydroxyheptyl methacrylate. Although one of ordinaryskill in the art will recognize that many different hydroxy-substitutedalkyl (meth)acrylates including those listed above could be employed,the preferred hydroxy functional monomers for use in the resin of thisinvention are hydroxy-substituted (meth)acrylates, meaning alkylacrylates and methacrylates having a total of 5 to 7 carbon atoms, i.e.,esters of C₂ -C₃ dihydric alcohols and acrylic or methacrylic acids.

Most preferably, the hydroxy-substituted alkyl (meth)acrylate monomercomprises a compound of the formula (III): ##STR5## wherein R⁴ ishydrogen or methyl and R⁵ and R⁶ are independently selected from thegroup consisting of hydrogen and alkyl of from 1 to 6 carbon atoms.Illustrative of these particularly suitable hydroxy-substituted alkyl(meth)acrylate monomers are 2-hydroxy ethyl methacrylate, 2-hydroxyethylacrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate and2-hydroxy-1-methylhexyl acrylate.

Among the non-hydroxy substituted alkyl (meth)acrylate monomers whichmay be employed are (meth)acrylates (as before, meaning esters of eitheracrylic or methacrylic acids) as well as mixtures of acrylates and vinylhydrocarbons. Preferred non-hydroxy unsaturated monomers are esters ofC₁ -C₁₂ monohydric alcohols and acrylic or methacrylic acids, e.g.,methylmethacrylate, ethylacrylate, butylacrylate, butylmethacrylate,hexylacrylate, 2-ethyl-hexylacrylate, lauryl-methacrylate, glycidylmethacrylate, etc.

Particularly preferred non-hydroxy substituted monomers are compoundsselected from the group consisting of monomers of the formula (IV):##STR6## wherein R⁷ is alkyl of from 1 to 6 carbon atoms and R⁸ ishydrogen or methyl. Particularly preferred are butyl acrylate, butylmethacrylate and methyl methacrylate.

The total monomer mixture passed to the polymerization process step willgenerally comprise from about 5 to 40 wt.%, and preferably from about 10to 30 wt.%, of the hydroxy-substituted alkyl (meth)acrylate and fromabout 5 to 95 wt.%, preferably from about 60 to 90 wt.% of thenon-hydroxy substituted alkyl (meth)acrylate monomer, in addition to anyoptional monomers (discussed below). The non-hydroxy substituted(meth)acrylate will typically comprise a mixture of methyl meth-acrylateor methyl acrylate, which will be present in an amount of from about 5to 30 wt.%, more preferably from about 10 to 25 wt.%, of the totalmonomer mixture, and up to about 60 wt.%, more preferably from about 25to 45 wt.%, of the total monomer mixture of butyl acrylate, butylmethacrylate, or mixtures thereof.

Additional optional monomers which can be employed in the polymerizationare monovinyl aromatic hydrocarbons containing from 8 to 12 carbonatoms, including styrene, alpha-methyl styrene, vinyl toluene, t-butylstyrene, chlorostyrene and the like. Where employed, these optionalmonovinyl hydrocarbons will be generally present in an amount of fromabout 5 to 30 wt.%, preferably from about 10 to 20 wt.% of the totalmonomer mixture.

In addition, other modifying monomers such as vinyl chloride,acrylonitrile, methacrylonitrile, vinyl acetate and acrylic acid mayalso be present. In the case of acrylic acid, when employed, thismonomer will generally be present in an amount from about 2 to 5 wt.% ofthe total monomer mixture. The remaining above-mentioned modifyingmonomers will generally be present in an amount of from 3 to 10 wt.% ofthe monomer mixture, where employed.

The ester polymerization solvent of this invention can be used alone oradmixed with other solvents such as ketones, ethers, alcohols, aromaticsolvents, and the like. Suitable ketone solvents are methyl amyl ketone,methyl isobutyl ketone, methyl propyl ketone and the like. Suitableether solvents are glycol ether acetates (e.g., ethoxy ethanol acetate,methoxy propanol acetate and the like). Suitable aromatic solventscomprise at least one aromatic hydrocarbon solvent containing as amajority component an alkyl-substituted benzene in which the alkylsubstituent comprises a total of at least 2 carbon atoms when thebenzene ring is mono-alkyl substituted and of at least 3 carbon atomswhen the benzene ring is substituted by two or more alkyl groups. Morepreferably, the aromatic solvent component comprises analkyl-substituted benzene of the formula (V): ##STR7## wherein p is aninteger of from 1 to 4, and X is in each instance in which it appearsindependently selected from the group consisting of straight andbranched-chain alkyl of from 1 to 4 carbon atoms, with the proviso thatwhen p is 1, X must contain at least 2 carbon atoms and with the furtherproviso that when p is 2 or greater, the X groups must contain a totalof at least 3 carbon atoms, and mixtures of the foregoing aromaticcompounds.

Illustrative of suitable alkyl-substituted benzene solvents for use inthe solvent blends of this invention are ethyl benzene, isopropylbenzene, n-propyl benzene, 1-methyl-3-ethylbenzene,1-methyl-4-ethylbenzene, 1,3,5-trimethylbenzene,1-methyl-2-ethylbenzene, 1,2,4-trimethylbenzene, isobutylbenzene,sec-butylbenzene, 1-methyl-3-isopropylbenzene,1-methyl-4-isopropylbenzene, 1,2,3-trimethylbenzene,1-methyl-2-isopropylbenzene, 1,3-diethylbenzene,1-methyl-3-n-propylbenzene, n-butylbenzene, 1,4-diethylbenzene,1,3-dimethyl-5-ethylbenzene, 1,4-dimethyl-2-ethylbenzene,1,3-dimethyl-4-ethylbenzene, 1,2-dimethyl-4-ethylbenzene,1,2,4,5-tetramethylbenzene, 1,2,3,5-tetramethylbenzene and the like, andmixtures of the foregoing.

The aromatic solvent component can also contain up to about 50 wt.%,preferably less than about 40 wt.%, and more preferably up to about 25wt.%, of other hydrocarbon solvents such as C₆ to C₁₄ aromatic solventsnot satisfying the definition of formula III above, as well as C₆ to C₁₄saturated aliphatic and cycloaliphatic hydrocarbons.

Especially preferred such polymerization solvent mixtures are thosewherein the higher liquid esters of this invention comprise at leastabout 40 wt.%, and more preferably from about 60 to 80 wt.%, of thesolvent mixture, and an aromatic solvent of formula (V) comprises up toabout 60 wt.%, and more preferably from about 20 to 40 wt.%, of thesolvent mixture.

In preparing the polymers of this invention, the selected monomers,including the required hydroxy-substituted alkyl (meth)acrylate, andnon-hydroxy substituted alkyl (meth)acrylate, together with anymodifying or other monomers, may be mixed and reacted by conventionalfree radical initiated polymerization in such proportions as to obtainthe copolymer desired, this reaction being effected in the presence ofthe ester solvent of this invention. A large number of free radicalinitiators are known in the art and are suitable for the purpose. Theseinclude: benzoyl peroxide; lauryl peroxide; t-butylhydroxy peroxide;acetylcyclohexylsulfonyl peroxide; di-isobutyryl peroxide;di-(2-ethylhexyl)peroxydicarbonate; diisopropylperoxydicarbonate;t-butylperoxypivalate; decanoyl peroxide;azobis-(2-methylpropionitrile); 2-t-butylazo-2-cyanobutane; tertiarybutyl perbenzoate, etc. dicumyl peroxide, ethyl3,3-(t-amylperoxy)butyrate, ethyl 3,3-di(t-butylperoxy)butyrate, t-butylcumyl peroxide, and di-butyl cumyl peroxide, and di-t-butyl peroxide,and other dialkyl peroxides, peroxy ketals, and t-amyl peroxides.

The total monomer mixture to be employed in preparing the polymersaccording to the process of this invention will generally comprise fromabout 30 to 95 wt.%, preferably from about 50 to 90 wt.%, of the totalmass of monomers and solvent passed to the polymerization reactionvessel. Thus, the ester solvents of this invention will generallycomprise from about 10 to 70 wt.%, preferably from about 10 to 50 wt.%,of the total mass of monomers and solvent passed to the polymerizationvessel. The quantity of free radical initiators employed as catalyst inthe reaction can also vary widely and will generally be present in anamount of from about 0.5 to 6 wt.% of the total monomer componentscharged to the reaction mixture.

The conditions of temperature and pressure for conducting thepolymerization reaction can vary widely. Generally, the polymerizationwill be conducted at a temperature of from about 125° to 240° C. (andpreferably from about 4° to 210° C.) at atmospheric pressure. Pressuresof from about 10 to 500 psig are entirely suitable, although higher orlower pressures can be employed. The polymerization reaction can becarried out in any of the conventional equipment employed by theindustry for such reactions. Thus, the reaction vessel can comprise astirred reactor in which an inert atmosphere (e.g., N₂,Ar) is maintainedduring the polymerization to avoid reactions which gaseous oxygen whichcompete, or interfere, with the desired polymerization reaction.

The polymerization process can be carried out batchwise,semi-continuously, or continuously. The monomers and solvent can bepremixed or passed separately to the polymerization vessel alone, or incombination with the free radical initiators and other components.

The time for which the polymerization reaction is allowed to proceed canalso vary widely and will generally range from about 0.5 to 10 hours,preferably from about 1 to 6 hours.

The acrylic resins produced by the process of this invention aregenerally characterized by weight average molecular weights (M_(w)) fromabout 800 to 12,000, and preferably from about 1,000 to 10,000, and moregenerally from about 1,000 to 8,000. Also, the acrylic resins producedby the process of this invention will be generally characterized bynumber average molecular weights (M_(n)) falling with a range of fromabout 500 to 6,000, and more typically from about 700 to 3,500, and byM_(w) /M_(n) ratios of from about 1 to 5, and more typically from about1 to 4. Furthermore, the acrylic resins of the present invention will begenerally characterized by kinemmatic viscosities of up to 6,000 cs, andmore typically from 100 to 5,000 cs (as determined by ASTM D445). Theseacrylic resins can then be employed in the formulation of coatings withor without the addition of other solvents. The components of suchcoating compositions formulated using these acrylic resins can be any ofthe conventional catalysts, antioxidants, UV absorbers and stabilizers,surface modifiers, wetting agents as well as pigments. These materialsare conventional and a more complete description thereof is notnecessary for a full understanding of this invention. For example,illustrative conventional UV absorbers and stabilizers are illustratedby those discussed in European Patent Application No. 29,594.

The coatings prepared by use of the acrylic resins of this invention canbe applied to substrates, such as automobiles and the like, usingconventional methods known to the art, such as roller coating, spraycoating, electrostatic spray coating, dipping or brushing. Of course,the particular application technique will depend on the particularsubstrate to be coated and the environment in which the coatingoperation is to take place. A particularly preferred technique forapplying the high solids compositions, particularly when applying thesame to automobiles as top coats, is spray coating through the nozzle ofa spray gun.

In accordance with another embodiment of the present invention, animproved method for formulating a high solids acrylic resin coating,intended for use in electrostatic spray applications, is providedwherein the acrylic resin, which is formed by conventional techniques orby use of the aforementioned improved polymerization process using anester solvent of this invention, is formulated into a high solidscoating by use of a normally liquid ester solvent selected from thegroup consisting of compounds having the formula (I), as defined above.The normally liquid ester solvent can be employed in an amount of fromabout 10 wt.% to about 90 wt.% of the as-formulated coating composition,which is preferably formulated to contain high solids (that is, at leastabout 50 wt.% solids) and preferably from about 50 to 90 wt.% solids,and most preferably from about 55 to 80 wt.% solids.

As with the previously discussed embodiment of this invention, theacrylic resin and ester coating solvent of this invention can beemployed in combination with any of the conventional catalysts,anti-oxidants, UV absorbers and stabilizers, surface modifiers, wettingagents and pigments which are known in the art. These materials, again,are conventional and a more complete description thereof is notnecessary for full understanding of this invention. For example,illustrative conventional UV absorbers and stabilizers are thoseillustrated by the discussion of European Patent Application No. 29,594and by the surface modifiers and pigments described in European PatentApplication No. 29,339, the disclosures of which are hereby incorporatedby reference.

The coating which is so formulated can also contain the selectednormally liquid ester solvent of this invention in combination with anyof the above-discussed solvents which are capable of use aspolymerization co-solvents, or sole solvents. Among these additionalcoating co-solvents are toluene, xylene, acetone, methyl isobutylketone, methyl ethyl ketone, butyl alcohol, aromatic solvents, aliphaticsolvents, cycloaliphatic solvents, cumene, methyl amyl ketone, and thelike which are conventionally used in coating compositions.

The novel coating compositions of this invention can be applied to avariety of substrates such as metal, wood, glass and plastics such aspolypropylene, styrene, polyurethane and copolymers of styrene, by anyof the usual application methods such as by spraying, electrostaticspraying, dipping, brushing, flow coating, rolling and the like. Mostpreferably, the novel coating compositions of this invention are appliedby electrostatic spraying.

The thus-formed coatings can be air-dryed or baked. The resultingcoating is preferably from about 0.2 to 3 mils thick, and preferably 0.4to 2.5 mils thick, and can be rubbed or polished in accordance withconventional techniques, if desired, to improve smoothness or apparentgloss or both.

After the novel coating composition is applied, the coating ispreferably cured at about 80° to 210° C. for about 5 to 45 minutes.Typical catalysts that can be used are butyl acid phosphate, paratoluenesulfonic acid, naphthalene sulfonic acid and naphthalene disulfonicacids (as described in U.S. Pat. Nos. 3,979,478 and 4,075,176), aminesalts of any of the foregoing, and the like.

The process and compositions of this invention can be furtherillustrated by reference to the following examples, wherein parts are byweight unless otherwise indicated.

In the Examples, unless otherwise indicated, the following testprocedures or devices were used for determining the correspondingproperties:

                  TABLE 1                                                         ______________________________________                                        Property Measurement                                                                           Test Method/Device                                           ______________________________________                                        Impact resistance (reverse)                                                                    ASTM D2794-69                                                Gloss            ASTM D523                                                    Viscosity        Zahn cup #2, ASTM D3794; or                                                   Ubbelohde viscometer, ASTM                                                    D445                                                         Pencil Hardness  ASTM D2794-69                                                Flash Point (TCC)                                                                              ASTM D-56                                                    Electrical Resistivity                                                                         Ransburg 5650 paint resistance                                                tester (manufactured by                                                       Ransburg)                                                    Film Thickness   ASTM D1186, modified by use                                                   of a Positector 2000 (manu-                                                   factured by KTA-Tator, Inc.)                                                  Magnetic digital thickness                                                    meter                                                        Color            ASTM D2849 (Gardner color                                                     scale)                                                       Evaporation rate ASTM D3539-76 (Method B)                                     Surface Tension  ASTM D1331                                                   Appearance       Visual examination of paint                                                   film for smoothness; absence                                                  of pinholes, cratering,                                                       orange peel and wrinkling.                                   ______________________________________                                    

Percent solids reported in the Examples are nominal solids, calculatedbased on the amount of solids added to the recited mixtures.

The primary amyl acetate used in the Examples is manufactured by UnionCarbide Corporation and is a mixture of 2-methyl-butyl acetate,3-methyl-butyl acetate and n-pentyl acetate. The hexylacetate andheptyacetate used in the Examples were products of an esterificationreaction between acetic acid and the corresponding hexyl or heptylalcohol. The alcohol precursors themselves were formed in a commercialoxo reaction and each comprised a mixture of normal- and iso-alcohols.(Similar results would be achieved if pure normal- or iso-hexyl orheptyl alcohols were used.)

In the Examples, AROMATIC™ 100 solvent (manufactured by Exxon CompanyUSA) comprised a narrow-cut aromatic solvent containing about 40 wt. %trimethyl benzenes, 35 wt. % methyl ethyl benzenes, 10 wt. % propyl andisopropyl benzenes, 3 wt. % ethyl dimethyl benzenes, 2 wt. % methyl (n-and iso-) propyl benzenes, 2 wt. % diethyl benzenes, <1 wt. % each ofmono butyl benzenes and tetramethyl benzenes, 6 wt. % xylenes and minoramounts of ethyl benzene, C₁₀ and C₁₁ saturates and unknowns.

Number average molecular weights (M_(n)) and weight average molecularweights (M_(w)) were found by gel permeation chromatography.

EXAMPLE 1

To a five liter flask equipped with a mechanical stirrer, an additionfunnel and a reflux condenser was added, in a series of runs, 350 gramsof the selected ester solvent and 150 grams of AROMATIC™ 100 solvent(Exxon Company USA) as the polymerization solvent. The addition funnel(2 liter capacity) contained:

                  TABLE 2                                                         ______________________________________                                                           Grams Wt. %                                                ______________________________________                                        2-hydroxyethyl methacrylate                                                                        240     20                                               Methyl methacrylate  240     20                                               Styrene              120     10                                               Butyl acrylate       568     47.3                                             Acrylic acid          32     2.7                                                                   1,200   100.0                                            ______________________________________                                    

Added to the above mixture in the addition funnel was 56 grams oft-butylperbenzoate. The liquids in the two addition funnels and in thereaction flask were kept under a nitrogen blanket (1 atm. N₂). Thesolvent blend in the reaction flask was heated at the indicated reactiontemperature and the contents of the two funnels were added slowly, withstirring over a period of 2 hours. After completion of the addition,stirring and heating was continued for an additional one-half hour. Then4 more grams of t-butyl perbenzoate dissolved in a blend of 14 gms ofthe selected ester solvent and 6 gms of AROMATIC 100 solvent were addedin small portions and stirring and heating was continued for 1/2 hour tocomplete the polymerization. The thus-produced polymerized resins werethen tested for their physical properties, yielding the data set forthin Table 3 below:

                                      TABLE 3                                     __________________________________________________________________________    Polymerization in Ester Solvent/                                              Aromatic Solvent Blends                                                                Run No.                                                                       1-1 1-2    1-3   1-4 1-5 1-6                                                  n-butyl                                                                           primary amyl                                                                         iso-butyl                                                                           hexyl                                                                             heptyl                                                                            heptyl                                      Ester Solvent:                                                                         acetate                                                                           acetate                                                                              iso-butyrate                                                                        acetate                                                                           acetate                                                                           acetate                                     __________________________________________________________________________    Resin Properties                                                              Resin Viscosity                                                                        8,640                                                                             4,180  5,337 3,940                                                                             4,739                                                                             2,655                                       (1) (CS)                                                                      Color Gardner                                                                          <1  <1     <1    <1  <1  <1                                          Electrical                                                                             >20 >20    >20   >20 >20 >20                                         Resistivity                                                                   (Megohms)                                                                     Polymer Solids                                                                         70  70     70    70  70  70                                          (wt. %)                                                                       M.sub.w  15,789                                                                            7,044  7,070 5,790                                                                             6,168                                                                             5,097                                       M.sub.n  2,620                                                                             1,660  1,550 1,600                                                                             1,800                                                                             1,285                                       M.sub.2 /M.sub.n                                                                       6.0 4.2    4.5   3.6 3.4 3.9                                         Reaction 136.sup.(2)                                                                       146.sup.(2)                                                                          151.sup.(2)                                                                         150 150 162                                         Temp. (°C.)                                                            __________________________________________________________________________     (1) Measured as kinematic viscosity, obtained with an Ubbelohde               viscometer, ASTM D445.                                                        (2) Reflux temperature.                                                  

From the data in Table 3 it can be seen, therefore, that the estersolvents of this invention (Runs 1-2 through 1-6) provide significantlyenhanced resin properties and permit the formation of high solids resinsolutions characterized by lower resin viscosities, much lower weightaverage molecular weights and narrower molecular weight distribution(i.e., lower M_(w) /M_(n) ratios). The solvents of this inventionprovide acrylic resins which are uniquely suited for use in electrosprayhigh solids applications.

EXAMPLE 2

The polymerized resins obtained in Example 1 (without removal of thepolymerization solvent) were then used to formulate a series of paintcoating compositions employing the selected coating solvent and theadditional coating ingredients identified in Table 4.

                  TABLE 4                                                         ______________________________________                                                   Runs 2-1 to 2-5:                                                                          Run 2-6                                                           wt. (gms)                                                                            wt. %    wt. (gms)                                                                              wt. %                                     ______________________________________                                        Resin.sup.(1)                                                                              309.4    36.4     340    40.0                                    Ester solvent                                                                              151.3    17.8     125    14.7                                    AROMATIC 100 56.1     6.6      41.7   4.9                                     n-Butanol    40.0     4.7      33.1   3.9                                     CYMEL 303.sup.(2)                                                                          85.0     10.0     93.5   11.0                                    TiO.sub.2.sup.(3)                                                                          204.0    24.0     212.5  25.0                                    BYK Catalyst 451.sup.(4)                                                                   4.2      0.5      4.2    0.5                                     Total        850.0    100.0    850.0  100.0                                   ______________________________________                                         .sup.(1) Resin as charged included the polymerization solvent.                .sup.(2) Hexamethoxymethyl melamine, 100% solid resin (produced by            American Cyanamid) as crosslinking amino resin.                               .sup.(3) Tipure (E.I. Dupont de Nemours, Pigments Division) as pigment.       .sup.(4) pToluene sulfonic acid, 30% solution in isopropanol, neutralized     with pyridine (Mallincrodt), as cure catalyst.                           

In each run, the selected resin and ester coating solvent, together withthe remaining Table 4 components (other than the BYK cure catalyst),were placed in a ceramic pebble mill (Paul O. Abbe, Inc., Little Falls,N.J.) which was then rolled on mill rollers for a time of 12 hours. Theliquid coating was then filtered using a Gardco paint filter; fine-60×45mesh to remove gel particles, and then mixed with the cure catalyst toform the paint coating composition. Each paint coating composition wastested to determine its physical properties (giving the data summarizedin Table 5), and then employed to form a 3 mil (wet) film on selectedflat, substrate panels using a drawdown blade. After baking of thedrawdown films in an oven at 350° F. for 15 minutes, the dried paintfilms were then tested, again giving data summarized in Table 5.

The data in Table 5 illustrate the improved liquid coating viscositiesobtained with ester solvents of this invention at equivalent solidslevels to the prior art butyl acetate solvent. This can be seen incomparing the viscosities of Runs 2-2 through 2-5 with the viscosity ofthe liquid coating formulated in Run 2-1.

                                      TABLE 5                                     __________________________________________________________________________    Paint Formulations and Surface Film                                                           Run No.:                                                                      2-1 2-2    2-3   2-4 2-5 2-6                                                  Resin Prepared in Run No.:                                                    1-1 1-2    1-3   1-4 1-6 1-6                                                  n-butyl                                                                           primary amyl                                                                         iso-butyl                                                                           hexyl                                                                             heptyl                                                                            heptyl                               Ester Coating Solvent:                                                                        acetate                                                                           acetate                                                                              isobutyrate                                                                         acetate                                                                           acetate                                                                           acetate                              __________________________________________________________________________    Properties of Liquid Coating:                                                 Electrical resistivity (megohms)                                                              1.3 1.6    1.7   1.8 1.7 2.0                                  Viscosity Zahn #2 (sec.)                                                                      24.7                                                                              21.8   21.6  21.0                                                                              20.8                                                                              27.1                                 Percent solids (wt %)                                                                         60  60     60    60  60  65                                   Flash Point (°F.)                                                                      81  90     87    99  101 --                                   Film Properties:.sup.(1)                                                      Gloss 20°                                                                              74  74     71    76  75  68                                   60°      91  91     89    92  91  91                                   Impact resistance (in-lbs)                                                                    80  80     80    82  92  84                                   Pencil hardness 3H  2H     2H    2H  2H  3H                                   Appearance      good                                                                              poor   good  good                                                                              good                                                                              good                                 __________________________________________________________________________     .sup.(1) Determined using phosphatized steelpanels (Bonderite ® 40        treated; manufactured by Parker Chemical Co.) as the substrate on which       drawdown films were formed.                                              

EXAMPLE 3

A series of eight resins were formed using the polymerization procedureof Example 1 except that the polymerization solvent comprised 520 gramsof the selected liquid ester solvent at the reaction temperatures,indicated in Table 6.

The thus-produced resins were then tested for their physical properties,yielding the data set forth in Table 6 below.

As can be seen from the data set forth in Table 6, the ester solvents ofthis invention in Runs 3-2 through 3-8 are superior polymerizationsolvents in forming the high solids acrylic resins. The resinviscosities are significantly reduced when the ester solvents of thisinvention are employed, as compared to the unacceptably high resinviscosity achieved by use of the prior art butyl acetate in Run 3-1. Inaddition, the ester solvents of this invention achieved greatly loweredweight average molecular weights and narrower molecular weightdistributions than were obtained in the use of the butyl acetatessolvents in the above described acrylic polymerizations.

                                      TABLE 6                                     __________________________________________________________________________    Polymerization in Ester Solvents                                                         Run No.                                                                       3-1 3-2    3-3   3-4 3-5 3-6 3-7 3-8                                          n-butyl                                                                           primary amyl                                                                         iso butyl                                                                           C.sub.5 /C.sub.8                                                                  hexyl                                                                             hexyl                                                                             heptyl                                                                            heptyl                            Ester Solvent:                                                                           acetate                                                                           acetate                                                                              isobutyrate                                                                         blend.sup.(1)                                                                     acetate                                                                           acetate                                                                           acetate                                                                           acetate                           __________________________________________________________________________    Resin Properties:                                                             Resin viscosity                                                                          20,550                                                                            4,430  5,380 3,135                                                                             4,179                                                                             2,460                                                                             5,953                                                                             1,968                             (cs) (3)                                                                      Color (Gardner)                                                                          <1  <1     <1    <1  <1  <1  <1  <1                                Percent Solids (wt %)                                                                    70  70     70    70  70  70  70  70                                Mw         57,949                                                                            10,687 9,978 6,168                                                                             7,283                                                                             5,310                                                                             7,679                                                                             3,857                             Mn         2,912                                                                             2,500  1,676 1,649                                                                             1,583                                                                             1,587                                                                             1,949                                                                             1,313                             Mw/Mn      19.9                                                                              4.2    5.9   3.7 4.6 3.3 3.9 2.9                               Reaction Temp.(°C.)                                                               132.sup.(2)                                                                       145.sup.(2)                                                                          149.sup.(2)                                                                         159.sup.(2)                                                                       150 162.sup.(2)                                                                       150 168.sup.(2)                       __________________________________________________________________________     .sup.(1) 50:50 wt.:wt. blend of primary amyl acetate and 2ethylhexyl          acetate.                                                                      .sup.(2) Reflux temperature.                                                  .sup.(3) Measured as kinematic viscosity, obtained with an Ubbelohde          viscometer.                                                              

EXAMPLE 4

A series of five resins (Runs 4-1 through 4-5) were formed using thepolymerization procedure of Example 1 except that the polymerizationsolvent comprised 520 grams of methyl amyl ketone and the reactiontemperature for each was 147° C.

Thereafter, paint coating compositions were formulated using theprocedure of Example 2, except that the coating ingredients were asidentified in Table 7 below:

                  TABLE 7                                                         ______________________________________                                                   Run 4-1     Runs 4-2 to 4-5                                                   wt. (gms)                                                                             wt. %   wt. (gms) wt. %                                    ______________________________________                                        Resin.sup.(1)                                                                              1,237.6   36.4    1,237.6 36.4                                   Coating Solvent.sup.(4)                                                                    605.2     17.8    605.2   17.8                                   VARSOL - 18.sup.(2)                                                                        224.4     6.6     --      --                                     AROMATlC 100 --        --      224.4   6.6                                    n-Butanol    160       4.7     160     4.7                                    CYMEL 303.sup.(3)                                                                          340       10.0    340     10.0                                   TiO.sub.2.sup.(3)                                                                          816       24.0    816     24.0                                   BYK Catalyst 451.sup.(3)                                                                   16.8      0.5     16.8    0.5                                    Total        3,400.0   100.0   3,400.0 100.0                                  ______________________________________                                         .sup.(1) Resin as charged included the polymerization solvent.                .sup.(2) Hydrocarbon solvent (Exxon USA), 8% aromatic solvent (at least 8     or more carbon atoms per molecule), 92% saturated aliphatic hydrocarbons;     boiling range 156-204° C.                                              .sup.(3) For descriptions, see footnotes to Table 4 above.                    .sup.(4) As indicated in Table 8.                                        

In a separate run (Run 4-6), a paint coating composition was formedusing a resin prepared using the procedure of Example 1 (Run 1-4) using364 gms of hexyl acetate and 156 gms of AROMATIC 100 solvent as thepolymerization solvent blend, and a reaction temperature of 150° C. Thecoating composition was formulated using the procedure as described inExample 2 (Run 2-4). Thus, the coating solvent comprised a blend ofhexyl acetate, AROMATIC 100 solvent and n-butanol, as indicated in Table4 above for Run 2-4.

Each paint coating composition was tested to determine its electricalresistivity and viscosity, and then electrostatically sprayed ontopanels (fabricated from rolled steel Bonderite® 40 treated steel)using ahigh speed Turbobell (manufactured by Ransburg; model type: Monobell) at28,000 rpm, employing a spray voltage of 90,000 volts, a paint feed rateof 95 ml/min and a spray distance of 13 inches (from the panel to thesprayer). The panels were attached to a conveyor belt and passed by thesprayer at the rate of 15 linear feet per minute. The panels were coatedin 2 passes, with 2 minutes between the passes, and then allowed tostand for 5 minutes at ambient conditions after which the panels werebaked at 350° F. for 15 minutes in an oven. The data thereby obtainedare set forth in Table 8 below.

                                      TABLE 8                                     __________________________________________________________________________    Electrospray Coatings                                                                         Run No.:                                                                      4-1 4-2    4-3   4-4  4-5 4-6                                                 Polymerization Solvent:                                                       MAK MAK    MAK   MAK  MAK hexyl acetate                                           primary amyl                                                                         isobutyl                                                                            C.sub.5 /C.sub.8                                                                   hexyl                                                                             hexyl                               Coating Solvents:                                                                             MAK acetate                                                                              isobutyrate                                                                         acetate.sup.(1)                                                                    acetate                                                                           acetate                             __________________________________________________________________________    Properties of Liquid Coating                                                  Electrical resistivity (Megohms)                                                              0.10                                                                              0.35   0.35  0.40 0.40                                                                              1.8                                 Viscosity Zahn #2 (sec.)                                                                      21.4                                                                              21.2   21.8  22.3 21.7                                                                              21.6                                Film Properties                                                               Film Thickness (mil.)                                                                         1.0-1.2                                                                           1.0-1.2                                                                              1.0-1.2                                                                             1.0-1.2                                                                            1.0-1.2                                                                           1.0-1.2                             % Gloss 20°                                                                            47  66     60    72   70  74                                  60°      83  88     86    90   88  91                                  Impact resistance (in. lbs)                                                                   50  80     97    124  142 168                                 __________________________________________________________________________     MAK = methyl amyl ketone                                                      .sup.(1) 50:50 wt.:wt. blend of primary amyl acetate and 2ethylhexyl          acetate.                                                                 

From the data presented in Table 8, it is apparent that the estersolvents of this invention in Runs 4-2 through 4-6, when employed ascoating solvents for formulation of high solids electrostatic spraycoatings, provide formulated coatings of significantly enhancedelectrical resistivities as compared to the prior art methyl amylketone, and also enable the formation of electrostatically sprayed filmswhich provide superior gloss and impact resistance. The combined use ofthe ester solvents of this invention as both polymerization solvent andcoating solvent (Run 4-6) is especially superior in the resultingelectrical resistivity of the formulated coating and in the gloss andimpact resistance properties of the film achieved by electrostaticspraying of the thus-formulated coating.

EXAMPLE 5

The procedure of Example 1 was repeated in a series of five runs, exceptthat the polymerization solvent comprised 364 grams of methyl isobutylketone and 156 grams of cumene.

Thereafter, each resin was formulated into a paint coating compositionusing the procedure of Example 2, and the coating ingredients identifiedin Table 4 (Runs 2-1 through 2-5), with the selected ester coatingsolvent. Drawdown films were prepared from each paint coatingcomposition, again following the procedure of Example 2. The formulatedcoatings and the baked drawdown films were tested to determine theirproperties, thereby providing the data summarized in Table 9 below.

                                      TABLE 9                                     __________________________________________________________________________                    Run No.:                                                                      5-1   5-2    5-3   5-4   5-5                                                  n-butyl                                                                             primary amyl                                                                         isobutyl                                                                            hexyl heptyl                               Coating Solvent:                                                                              acetate                                                                             acetate                                                                              isobutyrate                                                                         acetate                                                                             acetate                              __________________________________________________________________________    Coating Properties:                                                           Evaporation rate of coating                                                                   67    40     45    21    11                                   solvent                                                                       Electrical Resistivity (Megohms)                                                              0.48  0.60   0.65  0.99  0.75                                 Viscosity, Zahn #2 (sec) 25° C.                                                        22    23.4   24.1  24.6  26.0                                 8° C.    29    34.6   39.1  38.9  43.4                                 Percent solids (wt. %)                                                                        60    60     60    60    60                                   Surface tension (dynes/cm.sup.2)                                                              30.9  30.9   29.4  30.9  31.0                                 Flash point (°F.)                                                                      76    82     78    82    86                                   Film Properties.sup.(1)                                                       Gloss 20°                                                                              65    73     70    75    69                                   60°      91    91     90    90    90                                   Impact resistance (in.-lbs)                                                                   116   94     72    164   66                                   Pencil hardness 3H    3H     3H    3H    3H                                   Appearance      acceptable                                                                          cratering                                                                            acceptable                                                                          acceptable                                                                          acceptable                           __________________________________________________________________________     .sup.(1) Observed on panels composed of phosphatized steel (Bonderite         ® 40, manufactured by Parker Chemical Co.). Acceptable appearance         films were observed on use of cold rolled steel panels with primary amyl      acetate.                                                                 

From the data set forth in Table 9, it is seen that the ester solventsof this invention, and particularly hexyl acetate, provide electricalresistivities which are superior to that of the prior art butyl acetate,and at the same time enables the formation of high gloss films with highimpact resistance. Hexyl acetate is particularly effective in forming afilm of superior impact resistance, as determined on the drawdown films.

EXAMPLE 6

To a five liter flask equipped with a mechanical stirrer, an additionfunnel and a reflux condenser was added, in a series of runs, 520 gramsof the selected higher alkyl ester solvent as the polymerizationsolvent. The addition funnel (2 liter capacity) contained:

                  TABLE 10                                                        ______________________________________                                                           Grams Wt. %                                                ______________________________________                                        2-hydroxyethyl methacrylate                                                                        240     20                                               Methyl methacrylate  240     20                                               Styrene              120     10                                               Butyl acrylate       568     47.3                                             Acrylic acid          32     2.7                                                                   1,200   100.0                                            ______________________________________                                    

Added to the above mixture in the addition funnel was 65 grams ofethyl-3,3-di(t-amyl peroxy) butyrate. The liquids in the two additionalfunnels and in the reaction flask were kept under a nitrogen blanket (1atm. N₂). The solvent blend in the reaction flask was heated at theindicated reaction temperature and the contents of the two funnels wereadded slowly, with stirring over a period of 4 hours. After completionof the addition, stirring and heating was continued for an additionalone-half hour. Then 4 more grams of ethyl-3,3-di(t-amyl peroxy) butyratedissolved in 20 gms of the selected ester solvent were added in smallportions and stirring and heating was continued for 1/2 hours tocomplete the polymerization. The thus-produced polymerized resins werethen tested for their physical properties, yielding the data set forthin Table 11 below:

                  TABLE 11                                                        ______________________________________                                        Polymerization in Ester Solvents                                                         Run No.:                                                                        6-1      6-2      6-3    6-4                                                  hexyl    heptyl   octyl  nonyl                                   Ester Solvent:                                                                             acetate  acetate  acetate                                                                              acetate                                 ______________________________________                                        Resin Properties                                                              Resin Viscosity                                                                            1,170    602      549    472                                     (1) (cs)                                                                      Color Gardner                                                                              <1       <1       <1     <1                                      Electrical   >20      >20      >20    >20                                     Resistivity                                                                   (Megohms)                                                                     Polymer Solids                                                                             67.5     65.3     66.2   65.4                                    (wt. %)                                                                       M.sub.w      4118     3028     2470   2181                                    M.sub.n      1953     1537     1310   1199                                    M.sub.w /M.sub.n                                                                           2.10     1.97     1.88   1.82                                    Reaction     157      169      182    196-204                                 Temp. (°C.)                                                            ______________________________________                                         (1) Measured as kinematic viscosity, obtained with an Ubbelohde               viscometer, ASTM D445.                                                   

EXAMPLE 7

A series of four resins were formed using the procedure of Example 6with the exception that the initiation catalyst was dicumyl peroxideinstead of ethyl-3,3-di(t-amyl peroxy) butyrate. The thus producedpolymerized resin were tested yielding the data set forth in Table 12.

As it can be seen in Tables 11 and 12 the resins produced in the higherester solvents of this invention have superior properties with lowmolecular weights and very narrow molecular weight distribution (M_(w)/M_(n)). Resin of this type are most appropriate for the formulation ofhigh solids coatings of low viscosities.

                  TABLE 12                                                        ______________________________________                                        Polymerization in Ester Solvents                                                       Run No.:                                                                      7-1   7-2        7-3     7-4                                                  hexyl heptyl     octyl   nonyl                                                acetate                                                                             acetate    acetate acetate                                     ______________________________________                                        Resin Visc.                                                                              1449    698        292   234                                       (cs)                                                                          Polymer Solids                                                                           66.3    65.8       64.8  63.2                                      (wt. %)                                                                       M.sub.w    4534    3278       1974  1818                                      M.sub.n    1676    1645       1053  1007                                      M.sub.w /M.sub.n                                                                         2.70    1.99       1.87  1.80                                      Polymerization                                                                           160°                                                                           170°                                                                              192°                                                                         204°                               Temp. (C.°)                                                            % Free Radical                                                                           5.4     5.4        5.4   5.4                                       Initiator (1)                                                                 ______________________________________                                         (1) Dicumyl Peroxide (Luperox ™ 500R, supplied by Luirdol Division of      Penwalt).                                                                

EXAMPLE 8

The polymerized resins obtained in Example 6 (without removal of thepolymerization solvent) were then used to formulate a series of paintcoating compositions employing the procedure of Example 2 and thecoating ingredients identified in Table 13.

                  TABLE 13                                                        ______________________________________                                                       wt. (gms)                                                                            wt. %                                                   ______________________________________                                        Resin.sup.(1)    1,463    41.6                                                Ester Solvent    364      10.3                                                AROMATIC 100     196      5.6                                                 n-Butanol        164.5    4.7                                                 CYMEL 303.sup.(2)                                                                              402.5    11.4                                                TiO.sub.2.sup.(3)                                                                              892.5    25.4                                                Cycat ™ 4040.sup.(4)                                                                         35      1.0                                                 TOTAL            3,517.5  100.0                                               ______________________________________                                         .sup.(1) Resin as charged included the polymerization solvent.                .sup.(2) Hexamethoxymethyl melamine, 100% solid resin (produced by            American Cyanamid) as crosslinking amino resin.                               .sup.(3) Tipure (E.I. Dupont de Nemours, Pigments Division) as pigment.       .sup.(4) Cycat ™ 4040 (American Cyanamid) as cure catalyst.           

                  TABLE 14                                                        ______________________________________                                        Formulated Coatings with Resins Made in Higher Ester Solvents                                 Polymerization Solvent                                                        Heptyl Octyl    Nonyl                                                         Acetate                                                                              Acetate  Acetate                                                       (Obtain in Run:)                                                                6-1      7-3      7-4                                                         Hexyl    Hexyl    Hexyl                                     Formulation solvent                                                                             Acetate  Acetate  Acetate                                   ______________________________________                                        Properties of liquid Coating.sup.(1)                                          Electrical Resistivity (Megohms)                                                                1.1      0.50     0.60                                      Viscosity Zahn #2 (sec.)                                                                        22.4     19.6     21.3                                      Percent solids (wt. %)                                                                          65       65       65                                        Film Properties.sup.(2)                                                       Pencil Hardness   2H       H        F                                         Appearance        good     good     good                                      ______________________________________                                         .sup.(1) Coatings were catalysed with 1% Cycat ® 4040 (American           Cyanamid cure catalyst)                                                       .sup.(2) Drawdown films were made on phosphatized steel panels (Bonderite     ® 40 treated; manufactured by Parker Chemical Company). Films baked a     300° F. for 30 min.                                               

It will be obvious that various changes and modifications may be madewithout departing from the invention and it is intended, therefore, thatall matter contained in the foregoing description shall be interpretedas illustrative only and not limitative of the invention.

What is claimed is:
 1. An improved process for forming acrylic copolymerresins suitable for electrostatic spraying in high solids coatingscontaining at least 50 wt. % solids which comprises contacting underpolymerizing conditions a polymerization mixture comprising at least onehydroxy-substituted alkyl(meth)acrylate monomer and at least onenon-hydroxy substituted alkyl(meth)acrylate monomer in the presence of afree radical initiator and a solvent therefor, said solvent beingemployed in an amount of from about 10 to 70 wt. % of the polymerizationmixture, and said solvent comprising at least one normally liquid esterselected from the group consisting of compounds having the generalformula: ##STR8## wherein R¹ is an alkyl of 1 carbon atom, and R" is astraight or branched chain alkyl of 8 to 9 carbon atoms, saidhydroxy-substituted alkyl(meth)acrylate monomer comprising about 5 to 40wt. % of the total monomers charged to said polymerization reaction, andsaid non-hydroxy substituted alkyl(meth)acrylate monomer comprising fromabout 5 to 95 wt. % of the total monomers charged to said polymerizationreaction.
 2. The process of claim 1 wherein said hydroxy-substitutedalkyl(meth)acrylate monomer comprises a memberselected from the groupconsisting of monomers of the formula: ##STR9## wherein R⁴ is hydrogenor methyl and R⁵ and R⁶ are independently selected from the groupconsisting of hydrogen and alkyl of from 1 to 6 carbon atoms.
 3. Theprocess according to claim 1 wherein said non-hydroxy substitutedalkyl(meth)acrylate monomer comprises at least one monomer of theformula: ##STR10## wherein R⁷ is alkyl of from 1 to 6 carbon atoms andR⁸ is hydroxy or methyl.
 4. The process according to claim 1 whereinester solvent is employed in admixture with at least onealkyl-substituted benzene solvent in which the alkyl substituent(s)contains a total of at least 2 carbon atoms when the benzene ring ismonoalkyl substituted and contains a total of at least 3 carbon atomswhen the benzene ring is substituted by two or more alkyl groups.
 5. Theprocess according to claim 4 wherein said alkyl-substituted benzenesolvent comprises at least 1 aromatic compound of the formula: ##STR11##wherein p is an integer of from 1 to 4, and X is in each instance inwhich it appears independently selected from the group consisting ofstraight and branched-chain alkyl of from 1 to 4 carbon atoms, with theproviso that when p is 1, X must contain at least 2 carbon atoms andwith the further proviso that when p is 2 or higher, the X groups mustcontain a total of at least 3 carbon atoms, and mixtures of theforegoing aromatic compounds.
 6. The process according to claim 1wherein said polymerization reaction is effected for a time of fromabout 0.5 to 10 hours.
 7. The process according to claim 1 wherein theacrylic polymer produced in said polymerization reaction ischaracterized by a weight average molecular weight of from about 8,000to about 12,000.
 8. A polymerizable composition comprising a mixture ofacrylic resin monomers and from about 5 to 70 wt. % of a solventcomprising at least one normally liquid ester selected from the groupconsisting of compounds having the formula: ##STR12## wherein R¹ is analkyl of 1 carbon atom, and R" is a straight or branched chain alkyl of8 to 9 carbon atoms.
 9. A polymerizable composition suitable forapplication after polymerization to a surface by electrostatic sprayingas a high solids coating which comprises(a) from about 30 to 45 wt. % ofa monomer mixture comprising(i) at least one hydroxy-substitutedalkyl(meth)acrylate in an amount of from about 5 to 40 wt. % of saidmonomer mixture; (ii) at least one non-hydroxy substitutedalkyl(meth)acrylate monomer in an amount of from about 5 to 95 wt. % ofsaid monomer mixture; and (iii) at least one free radical polymerizationinitiator in an amount of from about 0.5 to 6 wt. % of said monomermixture; and (b) from about 5 to 70 wt. % of a polymerization solventcomprising at least one normally liquid ester selected from the groupconsisting of compounds having the formula: ##STR13## wherein R¹ is analkyl of 1 carbon atom, and R" is a straight or branched chain alkyl of8 to 9 carbon atoms.
 10. The polymerizable composition of claim 9wherein said monomer mixture further comprises from about 5 to 30 wt. %of at least one monovinyl aromatic hydrocarbon containing from 8 to 12carbon atoms.
 11. Low viscosity acrylic resins, suitable forelectrostatic spraying as a coating containing at least 50 wt. % solidsupon a surface, which comprise resins formed by polymerization of fromabout 30 to 95 wt. % of an acrylic monomer mixture in the presence offrom about 5 to 70 wt. % of a polymerization solvent comprising at leastone normally liquid ester selected from the group consisting ofcompounds having the formula: ##STR14## wherein R¹ is an alkyl of 1carbon atom, and R" is a straight or branched chain alkyl of 8 to 9carbon atoms, said acrylic monomer mixture comprising:(i) at least onehydroxy-substituted alkyl(meth)acrylate in a mount of from about 5 to 40wt. % of said monomer mixture; (ii) at least one non-hydroxy substitutedalkyl(meth)acrylate monomer in an amount of from about 5 to 95 wt. % ofsaid monomer mixture; and (iii) at least one free radical polymerizationinitiator in an amount of from about 0.5 to 6 wt. % of said monomermixture,said acrylic resin being characterized by weight averagemolecular weights of from about 1,000 to 10,000 by kinematic viscositiesof up to 6,000 cs and by weight average molecular weight to numberaverage molecular weight ratios of from about 1 to
 5. 12. The lowviscosity acrylic resins of claim 11 wherein said acrylic monomermixture additionally comprises from about 5 to 30 wt. % of at least onemonovinyl aromatic hydrocarbon containing from 8 to 12 carbon atoms, andeither (i) from about 2 to 5 wt. % of acrylic acid, or (ii) from about 3to 10 wt. % of at least one member selected from the group consisting ofvinylchloride, acrylonitrile, methacrylonitrile and vinyl acetate.